Materials testing apparatus



June 14, 1938. TRQXELL, 2,120,381

MATERIALS TESTING APPARATUS Filed Oct. 9, 1935 2 Sheets-Sheet l as vINVENTOR June 14, 1938. G. E. TROXELL MATERIALS TESTING APPARATUS 1935 2Sheets-Sheet 2 Filed Oct. 9

INVENTOR 6. E. Trox y fl n 1 ATORN Y v Patented June 14, 1938 UNITED 'fSTATES PATENT- OFFICE Baldwin- Southwark Corporation, a

tion of Delaware corpora- I Application October 9,1935, Serial No.'44,23,3 1 Claims. (01. 265-14 This invention relates generally to animproved apparatus for controlling or regulating pressure or load or forcontrolling the application of power to a movable member which may servevarious purposes, one of which as specifically shown herein is to load aspecimen in a materials testing machine although certain principles andfeatures of the invention are broadly applicable to various deviceswhich may be either foreign or auxiliary to materials testing machinesand in.

which pressure or load is broadly a factor.

It is one object of my invention to provide an improved sensitiveapparatus for efi'ectively controlling or regulating pressure, load orthe application of power to a power driven movable memher. In onespecific aspect of the invention I have applied one form of theapparatus, to the control of a materials testing machine so as tomaintain a substantially constant load on a specimen and maintain suchload within relatively narrow limits at any selected value of the loadrange or to change the load at any desired rate. It will be understoodthat precision qualities and sensitiveness are vital to apparatus of anykind 25 which involves means responsive to the load of a specimen andthat it is always desirable that the initial load responsive elements ofsuch apparatus ,shall be as free as possible from friction or restraint.Any inaccuracies that may be present in 30 the initial load responsiveelements will be immediately reflected in a very much magnified mannerin the power movable member which it is desired to control. object of myinvention to accomplish this initial 35 load responsiveness with a greatdeal of sensitivity and accuracy and to precisely control a largersource of power.

. In a hydraulic materials testing machine a source of hydraulic poweris supplied to a load 40 producing cylinder and ram for stressing aspecimen. Due to leakage between the ram and cylinder or other possiblecauses, considerable difliculty may be experienced in maintainingconstant load on the specimen especially for an 46 appreciable period oftime.

In one specific application of my invention as herein disclosed I employa hydraulically operated load responsive member, such as an indicatinghand. The load responsive fiuid may be 60 taken either directly from theram cylinder of a hydraulic type machine, or in the case of the Emerytype materials testing machine the fluid may be taken from anindependent weighing system which is a characteristic of the Emery type55 machine, or in the case of mechanically operated Hence it is afurther specific specimen. I then place in eflective cooperativerelation to such a load responsive member, light sources andphotoelectric cells arranged to control application of power to amovable member which for purposes of illustration herein is a ram of amaterials testing machine but which might be a movable power drivenmember of any auxiliary apparatus: used in connection with a materialstesting machine and necessitating that the application of power becontrolled in accordance with specimen load.

Other objects and advantages will be more apparent to those skilled inthe art from the following description of the accompanying drawings inwhich:

Fig. 1 is a diagram of the circuits and control elements in my improvedcombination; L

Fig. 2 is a front elevation of the apparatus for establishing the limitswithin which load may be maintained;

Fig. 3 is a substantially vertical section taken on the line 3-3 of Fig.2;

Fig. 4 is an enlarged perspective of one of the light slots;

Fig. 5 is a diagrammatic outline of a materials testing machine to whichmy invention is applied for purposes of illustration.

The particular embodiment of the invention as shown herein is merely forthe purpose of illustrating certain principles of the invention togetherwith its application to one type and form of apparatus among possibleothers. To this end,

I have disclosed in Fig. 5 a diagrammatic out-' line of an Emery typematerials testing machine wherein a specimen I is suitably supported formovable power driven member or means of any suitable form is shownspecifically herein for purposes of illustration as a ram 8 This powerdriven means is arranged to move platen 3 upwardly to impose acompression load on the specimen, whereas in a tension test the specimenis supported by suitable grips between crosshead 2 and an upper loadingcrosshead 3a. A motordriven pump 3 preferably of the adjustable Hele-Shaw type supplies pressure fluid power to cylinder 3 through a pipeill. Suitable means, provided for establishing the degree of availablepower, is specifically shown as a manually adjustable discharge valveIna although the Hele- Shaw pump can also be adjusted to determine theavailable power. Mechanism for controlling the application of power tothe movable member is specifically shown herein as comprising a springclosed relief valve I2 adapted to by-pass fluid from pipe Hi to a pumpsump. Hence by suitably controlling the said power through operation ofsaid control mechanism, it is possible to control movement of member 3and specifically to maintain a predetermined load on a specimen. Theload on the specimen is transmitted through the sensitive frame of themachine to the hydraulic support I in which fluid pressure proportionalto the load is created and transmitted through a pipe 13 to a Bourdontube generally indicated at IS in Fig. 3. The Bourdon tube as shown inFig. 3 rotates a shaftlfi and a double end hand ll, the tube and handbroadly constituting means responsive to the load on the specimen.

Hand I1 is' placed in front of an opaque disc 13 which is preferablysupported at its circular edge by a series of rollers l3 to permitangular adjustment about the axis of shaft l3. A light slot 23 is formedat one portion of disc 13. To insure a relatively narrow beam of lightthrough said slot together with circumferential or angular adjustmentthereof, there is provided a relatively thick light ray guide 2| having,as shown in Fig. 4, circumferentially elongated holes 22 to receivescrews adapted for threaded engagement with disc l8. The elongated holes22 permit angular adjustment of the light slot to assist in establishingone limit within which load is maintained. The load responsive hand I!is of sumcient width as to be able to cover slot 23 and thus interceptlight from a suitable source such as an incandescent bulb 23 supportedin alignment with light slot 23. Bulb 23 is enclosed within a suitableopaque casing 24 which is secured in any suitable manner to the front ofdisc i3 so as to move therewith during adjustment thereof. A bracket 23,for supporting a photoelectric cell 25 in alignment with the light slot,

' is secured to the rear of disc l3. Thus it is seen that thephotoelectric cell 25, light ray slot 23, sourceof light 23 and disc 18will always be maintained in fixed relation with respect to each otherso as to be adjustable as a unit.

There is also provided another light ray guide 21, source of light 23and photoelectric cell 23 to establish the other load limit. The twoslots 20 and 21 are very nearly on the same diametral line, the actualoffset from the diameter being adjustable due to elongated screw holes22. For safety purposes, a guide 30, alight source 3| and aphotoelectric cell 32 are substantially offset from the slot 21. It willbe understood that the construction and arrangement of all of theforegoing light sources, light .guides and photoelectric cells have thesame unitary relation to disc l3 and are identical to the specificconstruction described in connection with light 23, guide 2i andphotoelectric cell 25 together with the supporting structure therefor sothat the whole is adjustable as a unit.

In describing the mode of operation of the circuits and apparatus asused in controlling a and connection to the hydraulic support.

materials testing machine in response to load on a specimen for thepurpose of maintaining a constant load thereon, the low, high and safetylimit; light vcontrol units are respectively indicated by the numeralsI, II and III. To load the specimen, pump 3 is started by closure of aswitch in a pump motor circuit, the contacts of a solenoid switch 36 inthis circuit being normally closed. In the circuit of said solenoid thecontacts of a solenoid switch 31 are normally closed but said circuit isopen by virtue of a line switch 33 being open thus permitting solenoidswitch 33 to be closed and cause operation of pump 3 which thereuponsupplies pressure fluid to ram cylinder 6. During this time by-passvalve [2 is closed so that by adjusting the degree of opening of valve10a or by'adjusting the stroke of pump 9, sufficient fluid is pumped toload the specimen. When the desired load is reached, then valve Illa isadjusted to reduce flow therethrough to the point where it justmaintains a constant load on the specimen. The specimen load isindicated on the usual load indicating dial 33 which, as shown in saidEmery patent, has its own Bourdon tube This Bourdon tube is separatefrom tube I5 and hand ll. During the foregoing loading period, Bourdontube I5' and hand I! will have moved in accordance with the load. Whenthe desired load is reached, the disc l3 of the load maintainerapparatus is rotated manually in a clockwise direction (Fig; 2) throughany suitable means such .as a handwheel 34, a shaft 35 and a bevel gear36. Gear 36 drives one of rollers l3 which is preferably a gear meshingwith peripheral gear teeth on disc l3 to rotate the same. The rotationof disc I8 is continued until one end of,hand I] of the load maintainerhas relatively passed light control unit III but before said end of thehand has reached light unit II. This position of hand I1 isdiagrammatically indicated in dotted lines at 33', Fig. 1. Switches 38,33 and 43 are then substantially simultaneously closed with the resultthat current from a main line 4| is supplied through switch 38 toenergize a transformer 42. The secondary circuit of this transformersupplies current to light sources 23, 23 and 3|. Flow of light throughlight guide 33 will permit cell 32 to cause energization of the solenoidofswitch 31 as from a battery 43. Contacts of switch 31 will thereuponopen, thus preventing energization of the solenoid of switch 33 at thetime of closure of switch 33. Hence the contacts of switch 36 willremain closed to permit the pump to continue operation. Light also flowsthrough guide 21 to permit cell 23 to cause energization of a solenoidof a switch 44, the circuit therefor being from battery 43 through awire 45, cell 29, a wire 43, solenoid of switch 44, and a wire 41 to theother side of battery 43. Simultaneously, flow of light through guide 23upon cell 25 establishes a circuit from battery 43 through wire 45 cell25 to a solenoid of a solenoid switch 43 and thence through wire 41 tothe other side of the battery. Energization of the solenoids of switches44 and 43 causes the same to open and close respectively. Theenergization of the foregoing solenoids merely places the controlcircuits in an initial operative condition. In order to establish thelower limit above which it is desired to maintain load on the specimen,the operator continues clockwise rotation of disc I3, Fig. 2. Duringthis rotation, hand I! will first intercept light through guide 21,thereby deenergizing solenoid of switch 44 and permitting its contactsto complete a circuit for a solenoid II as by wires 49 and 52.Energization of solenoid 5| causes closure of contacts 53 therebyestab-l, lishing a circuit for solenoid 54, through a wire 56, to openby-pass valve l2. While opening of this valve will immediately cause adecrease of load, yet the amount of fluid by-passed is so small that therate of decrease of load is sufficiently low as to permit continuedrotation of disc it until it just intercepts the low limit light guideand thereby-immediately recloses the by-passvalve with consequentincrease of load on the specimen. The foregoing reestablished circuit isas follows: When light guide 2|! is Just covered, cell and the solenoidof switch 48 are deenergized to permitits contacts to open therebydeenergizing solenoid 5| and opening contacts 53. Solenoid 54 is therebydeenergized and valve l2 closed by gravity or by fluid pressure, andhence the pump increases the load on the specimen.

.As the load increases on the specimen, hand I1 ,will move in aclockwise direction as viewed in Fig 2, this direction beingdiagrammatically indicated by arrow A in Fig. l. The hand thus movesaway from the light guide 20 and toward guide 21 with the result thatthe light beam through guide 20 energizes cell 25 to cause energizationof the solenoid of switch 46, thereby reclosing its contacts but withoutestablishing any circuit. As the load continues to increase on thespecimen, hand |1 will ultimately intercept the beam of light throughguide 21 and thus deenergizes cell 29 and the solenoid of switch 44. Thecontacts of switch 44 thereupon fall to. their closed position andestablish a circuit from one side of main line 4| through switch 39,solenoid 5|, across contacts of solenoid switch 48 (which were closedwhen hand l1 uncovered guide 20), wires 49 and 52, across the closedcontacts of solenoid switch 44 to the other side of the main line 4|.Energization of solenoid 5| closes contacts 53 and also closes a contact50. Thereupon solenoid 54 is energized to open by-pass valve l2. Aportion of the pressure fluid from the pump is thus by-passed so thatload on the specimen will decrease, if at-all, but in any event will notincrease. Any decrease in the application of load on the specimen willdepend usually upon the leakage between the ram and cylinder and uponthe adjustment of the pump or its, discharge valve Illa. However,assuming that for anyone of various causes, the load on the specimendecreases, then load responsive hand |1 will move away from light guide21 toward guide 20. When the beam of light thus energizes cell 29, thesolenoid of switch 44 is reenergized to open its contacts. However, theby-pass valve l2 will continue to be held open due to the fact thatcontact 50 was'closed upon energization of solenoid 5|. The holdingcircuit for solenoid 5| is now through switch 39, solenoid 5|, acrosscontacts of solenoid switch 48, wire 49, contact 50 to contacts 53 andwire 56 to the other side of the supply line. Thus solenoid 54 ismaintained energized so that by-pass valve I2 is in open position topermit the continued decrease in load on the specimen. Hand l1, movingin the direction of guide 20 as the load decreases, will again interceptthe light therethroughso as to cause closure of the by-pass valve in themanner previously described. 'Ihe cycle of control between the lower andupper limits 20 and 21 respectively is thereby established and this willbe maintained within extremely close limits depending upon the /distance11km guides 20 and n a. offset from a diametral line.

If for any reason the by-pass valve should not open when the lightthrough the upper limit switch 38, thus causing the contacts of solenoidswitch 38 to open and break the pump motor circuit to discontinueoperation of the pump.

To indicate when the by-pass valve is open-or closed, there is provided,Fig. 1', a pair of indicating lamps 60 :and Cl whose circuits arecontrolled by solenoid 54 through contacts 52 movable with the solenoidcore.

From the foregoing disclosure it is seen that the regulation of pressureor load or the application of power to a movable member is controlledautomatically in accordance with the pressure or load and that thiscontrol is effected without imposing any friction or restraint whatsoever upon the load responsive means which specifically is the Bourdontube I5 and hand l1. It is also seen that the power operated member inthe form of the hydraulic ram is made to follow the load controlresponsive operations with a high degree of precision and with completeflexibility throughout the full load range of the apparatus regardlessof other variable factors which may occur.

To change the pressure or load at any desired rate, the disc ll may berotated, at that rate through the shaft and gearing l9 and 35.

It will of course be understood that various changes in details ofconstruction and arrangement of parts may be made by those skilled inthe art without departing from the spirit of the invention as set forthin the appended claims.

I claim:

1. In combination, means responsive to load on a specimen stressed in amaterials testing machine, a power driven member, mechanism forcontrolling the application of power to said member, a plurality ofphotoelectric cells and light beam sources therefor whose beams areadapted to be alternatively intercepted by said load responsive meansupon occurrence of predetermined loads, and means whereby said cells areadapted to control said mechanism within the limits of saidpredetermined loads.

2. In combination, a materials testing machine having hydraulic loadproducing means for stressing a specimen, means for controlling theapplication of power to said load producing means, high and low loadlimit devices for controlling said power application, and meansresponsive to the load on a'specimen for controlling said high and lowlimit load-devices thereby to maintain load on a specimen within thelimits set by said devices.

3. The combination set forth in claim 2 further characterized by theprovision of means for setting said devices to operate at any selected alight beam source and a photoelectric cell of its own, and meansresponsive to the load on a specimen for controlling one or the other ofthe limits any increase of load on the specimen and I control of theother beam causes an increase of load on the specimen, thereby causingthe load on the specimen to be maintained within the limits set by saidlight sources.

5. The combination set forth in claim 4 further characterized by theprovision oi a safety circuit having a photoelectric cell and a lightbeam source therefor whose beam is adapted to be controlled to renderthe load producing means inoperative upon occurrence of a load in excessof a desired upper load limit.

6. A load control apparatus for a materials testing machine in which aspecimen is stressed comprising, in combination, a plurality ofphotoelectric cells and light beam sources, means for rotatablysupporting said cells and sources as a unit in fixed relative relationto each other, and

a member freely movable between said cells and their light sources so asto intercept one or the other beams thereoi automatically in accordancewith load on the specimen, said intercepting member being movable aboutthe axis 01' rotation of said unitary structure.

7. In combination, a materials testing machine having hydraulic loadproducing apparatus, a source or hydraulic power therefor, means wherebythe load on a specimen may be brought up to a substantiallypredetermined value, a relief valve

